A little matter of light

By Kruti Shrotri

Light and matter are very different: while light has no shape, size or mass, matter has all three. However, researchers have recently found a way to create matter from just pure light.

Light and matter are inextricably linked by the famous equation E=mc2, the brainchild of Albert Einstein in 1905. This equation essentially tells us that mass is a form of energy. Since light is also a form of energy, the equation implies that it is theoretically possible to transform light into mass, and mass into light.

In 1934, Gregory Breit and John Wheeler took Einstein’s equation one step further. They theoretically proved that pure light could be used to create electron-positron particle pairs, i.e. matter. But they also said that it would be “hopeless to try and observe [this] in laboratory experiments”. Why? In part, because it takes a very large amount of energy to create a very small amount of matter. For example, the amount of energy that could power 10 million homes for 3 years would be at most enough to create just 1kg of matter.

Pretty lights by Michael Jastremski.

However, a team of researchers, led by PhD student Oliver Pike of Imperial College London, have found a way to overcome these challenges by colliding together light from two different sources. The first source comes from a high-energy light beam, fired into a small gold can. The second source comes from the can itself, which is made to emit light as bright as starlight. Together, the two sources create enough light intensity to allow for the creation of 100,000 electron-positron particle pairs – or around one carbon atom’s worth of matter.

One carbon atom’s worth of matter may not seem like much to us, but for physicists it paves the way to a new age of high-energy particle physics. Whereas current particle colliders, like CERN’s ‘Large Hadron Collider’, work by smashing together particles, future colliders could be built to use pure light instead.


Image: Pretty Lights under Creative Commons License